package network;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;
import java.nio.charset.StandardCharsets;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: ASUS
 * Date: 2025-03-01
 * Time: 15:31
 */
// UDP 的 回显服务器
// 客户端发的请求是啥, 服务器返回的响应就是啥
public class UdpEchoServer {
    private DatagramSocket socket = null;

    public UdpEchoServer(int port) throws SocketException {
        socket = new DatagramSocket(port);
    }

    public void start() throws IOException {
        System.out.println("服务器启动!");
        while (true) {
            // 1. 读取请求, 并解析
            DatagramPacket requestPacket = new DatagramPacket(new byte[4096], 4096);
            socket.receive(requestPacket);
            String request = new String(requestPacket.getData(),0,requestPacket.getLength());
            // 2. 根据请求, 计算响应
            String response = process(request);
            // 3. 把响应写会客户端
            DatagramPacket datagramPacket = new DatagramPacket(response.getBytes(),
                    response.getBytes().length, requestPacket.getSocketAddress());
            socket.send(datagramPacket);
            System.out.printf("[%s:%d] req: %s, resp: %s \n", requestPacket.getAddress().toString(),
                    requestPacket.getPort(), request, response);
        }
    }

    public String process (String request) {
        return request;
    }
    public static void main(String[] args) throws IOException {
        UdpEchoServer server = new UdpEchoServer(9090);
        server.start();
    }
}
